In the field of automotive lighting, it is known to have DBL-type (dynamic bending light) bending headlamps or movable optical elements for the adaptive lighting functions of ADB (adaptive driving beam) lights.
To make the optical elements movable, it is common to use electric actuators comprising a motor and a gear assembly. In order to step down a maximum amount of the output movement from the motor in a minimum amount of space, it is known to provide the gear assembly with an endless screw at the output from the motor combined with spur gears transmitting the movement of the endless screw to the movable optical elements. However, to function efficiently and for reasons of mass-production, the actuators have amounts of toothing play, between the different elements of the gear assembly. These amounts of toothing play have a direct impact on the precision of positioning of the optical elements.
With the widespread use of LED lighting sources and the advent of laser sources, whose particular feature is to have a smaller and more concentrated light source, such amounts of play lead to significant errors in the positioning of the optical elements forming the beam.
With the aim of compensating for as much as possible of the play that the gear assembly comprises, it is known to position a spring in the vicinity of the spur gears of the gear assembly, transmitting the rotary movement to the optical elements. This spring presses the two spur gears against one another and thus compensates for a radial play between these two gears, that is, a play along an axis parallel to the axes of rotation of the two gears. However, this spring does not make it possible to eliminate the radial play of the endless screw, defined by an angle of rotation about the axis of the endless screw, or the axial play of the endless screw, defined by a translation parallel to the axis of rotation of the endless screw. Moreover, each of these two different types of play can independently have an influence on the radial position of the spur gear in contact with the endless screw and thus on the positioning of the movable optical elements.